Regulation of GLS1 Expression by Scleraxis in Cardiac Fibroblasts
Bibliographic record
Abstract
Cardiac fibrosis is characterized by the excessive deposition of extracellular matrix, including fibrillar collagens, proteoglycans, and fibronectin. This process is energy‐intensive for cardiac fibroblasts, however it remains unclear how these energy metabolic requirements are met. Liver fibrosis, and in particular collagen synthesis, has been shown to be dependent on glutaminolysis, in which glutamine is converted to glutamate by the enzyme glutaminase (GLS) with further conversion to a‐ketoglutarate to fuel oxidative metabolism via the tricarboxylic acid cycle, but a role for glutaminolysis in cardiac fibrosis remains to be demonstrated. We previously showed that scleraxis (Scx) is a transcription factor that is critically required for the conversion of cardiac fibroblasts to myofibroblasts, but its potential role in glutaminolysis in these cells is unknown. We report here that freshly‐isolated rat cardiac fibroblasts (P0 – unpassaged) passaged twice to become myofibroblasts (P2) show concomitant up‐regulation of Scx by 5‐fold and GLS1 by 4‐fold in P2 versus P0. Scx over‐expression induced a 20‐fold increase in GLS1 expression. To determine whether GLS1 expression is dependent on Scx, we examined GLS1 expression in activated mouse cardiac fibroblasts (P1) isolated from wild type or Scx knockout mice. Scx knockout attenuated GLS1 expression by almost 90%. TGFb is a potent inducer of cardiac fibrosis that both dramatically up‐regulates Scx expression, and requires Scx for many of its downstream effects. TGFb treatment of wild type mouse P1 activated fibroblasts doubled the expression of GLS1, but had no effect in Scx KO cells. In silico analysis revealed four putative Scx binding sites in the GLS1 promoter. While TGFb significantly up‐regulated expression of the myofibroblast marker periostin in cardiac fibroblasts, both scleraxis knockout and the glutaminase inhibitor CB‐839 attenuated this induction, indicating a failure to convert to myofibroblasts. These findings suggest that Scx regulates GLS1 expression to facilitate increased energy metabolism during cardiac fibroblast to myofibroblast conversion. Support or Funding Information Canadian Institutes of Health Research (PJT‐162422).
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How this classification was reachedexpand
Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.000 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one teacher head, not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".